The present invention relates to electrically operated valves of the type employed for controlling flow of engine coolant in a vehicle equipped with a heat exchanger such as a passenger compartment heater core. The heated engine coolant or hot water is typically circulated through the passenger compartment heater core upon opening of the valve and, circulation is prevented to the heater core upon closure of the valve, although the heater core remains filled with coolant.
In such automotive heater applications for a water valve, it has been found desirable to use a butterfly type valve to provide better flow velocity profile; and, the resultant flushing effect produced thereby in order to reduce the buildup of sediment and deposits in the heater core. A bypass circulation arrangement has also been found highly desirable for automotive heater core valving.
In modern automotive passenger compartment heating systems, it has been found desirable to provide for modulation of the heater core water valve in order to provide for the necessary response of the heating system to enable adequate regulation of the passenger compartment temperature. This is particularly desirable and necessary where the passenger compartment heating system employs a heater core fluidically in series with an air conditioning evaporator in the blower discharge plenum. In such series or "stacked-core" systems it has been found necessary to provide fine resolution of modulation of the water valve position where a butterfly type valve is employed in order to maintain adequate regulation of the passenger compartment temperature.
In order to provide fine resolution of the water valve position, it has been found desirable to employ an electric servomotor to control the position of the water valve. It has therefore been desired to provide a simple, reliable electrically operated bypass water valve which is low in manufacturing cost and yet provides a high degree of resolution of valve position with low power consumption.
It has further been desired to provide a butterfly type electrically actuated bypass water valve for vehicle passenger compartment heater cores which is simple to assemble during manufacture and which is constructed in a manner to minimize the effects of deposit buildup on the butterfly valve. Heretofore, butterfly type water valves employed for controlling flow to automotive passenger compartment heater cores have employed a metal butterfly plate attached to a metal shaft and typically seating against valving surfaces provided in a plastic valve body. This arrangement has been found to be particularly susceptible to leakage because the metal butterfly plate does not completely seal against the valve seating surface due to non-uniformities in the valve seating surface. Thus it has been desired to provide some resiliency in the butterfly plate.
Heretofore butterfly type water valves for controlling flow to automotive heater cores have necessitated that the metal butterfly plate be welded to the shaft upon insertion of the parts into the valve body and subsequently sonically vibrated to effect a seating of the butterfly against the valve seating surfaces of the valve body. This procedure has proved to be troublesome and costly in mass production and particularly in the high volume production of such valves required for heater cores used in vehicle passenger compartments.
It has thus been desired to provide a high resolution electrically-operated bypass type water valve for automotive heater core applications which is easily assembled and low in manufacturing cost, yet provides reliable sealing of the butterfly plate to prevent leakage of engine coolant to the heater core when the valve is in the closed position.